Television receiver



May 10, 1949. F. R. NORTON 2,470,048

TELEVISION RECEIVER Filed May 31, 1946 FRANKY R. uom'ou Pntenhad May 1Q 1949 mew Mile-m fdm:

Application 1mm, isle-emu No. new

(onus-g2) redirected to television mceiv- Morewpecineaflyitis directed to'ecomliina flfomviiieo coma-est control for tale-:-

noon-receivers:

Rienustormry; in Eviction-receiving to provide separate controls for picture contrast andtorht'ishmees-control; The-brithtness controlnormaily vm'iee'the'onntrol electrode Bias on the cathode rao 'tube and than meets the hackmllfltl'itnoss: The contrast control'then varieetlie video-or me to change the-amplitude oiflthe video-signal mliemtwtho plotine tube.- Oonventlonar contrast controls operoteby varyingthe' radio-frequency; intermediets-mm. o1 videc fl eduencr rain. or a combination of these.

The manipulation at these two centroid in order-tn" asatisiactory plotm-e under chanzihfeignal'conditions requires a: skilrwlifofi ieoiten beyond that oi the average person who penile-see" a television receiver. It would; of

beairradvantage to have aslnglecontrol would perform the two tiinctjione. and whiolrwoidd' maintain a standtrdcontraetum alt'signel conditions. i

f It is an ohiect ot'thie invention, therefore, to

provide a single control to controi'vliotli thedh tensi y of the-television picture endfthe contrast thereof as viowed'on a conventiouafcathodeeray true of picture tulle.

It is. a mrthenohieetoi this invention to eliminateone' or more of'the shortcomings of prior art arrangementrs.

, The nbo eandiurther oblootaendnovel teatures wllTmore tony appear fitmnthe following detailed description when the same is read in connection with the mompanylng drawings which illustrate two embodiments oi tbeinetant intention. It is to be exnreselmunderstood honever, that-the drawings are too purposes oi' illustration onlir. end are not intonded:as a definition ofitheilmits oi the invention, reierenceforthis W being had to the appended claims;

In the drawings:

Fig. 1 illustretes s. final video amplifier stage in accordance wlth'the invention; and

miilustrates a eecomdrembodimontof the me: mm e Referring now to Fig. I, there is illustrated a terminal III connected to the ungrounded end I l of a potentiometer I! through a condenser 18. The control electrode 14 of an electron discharge tube [5 is connected to the variable arm l6 oi! the potentiometer II. The end H of the potentiometer i2 is connected through a series oomcomprising a variable resistor. il and a fixed resistor l8. to-a. source" oi potentialn dloated +lBt The anode llioi the-tube; "455m netted to-theeememoanoe +B-throngh-mked resistor It, and bathe controleleotrodo 2l=oi '.a cathode,.m tube-fl.- The cathode I of the cathode roy'tuhe-is oonnectedsdirecflm tmtho aoarce oivoltase; and through-commoner. um around. The. cathode-wartime tube (decomnected; to ground. through or parallel comhinle tion comprising arr- Inland-A cond mn-IL six I I: nowthfl wmmn Q. trated .orransemenh it. will-he =seem than the bins between the eontrolleleetrodoand. the cathode oithe. cathode ray; tube is equaL torthevoltage drop the resistor lmdnetoourrentdzawn by; themode-oathdesoireuit o! the-tube l5. It will also be. seen .thatthlevoltageis also put signal or the tube lhbecaueerthe tenoletor-mls the plate load otthe time II. 'rhererorenltwwiilbeoecmth t the range of signai voltegeezappeorlnsbetween the'control electrode and cathode oiithecathode-ramtuhe will bedependent on. the average bios applied: to the source oi. video-money. sic-nail (not. shown). It-wlllibemanlieet that the amplitude oi, the videooienale ahpliedto'the'oontroi electrodeod the-tube ti, the toathe control electrode 23 of the cathode ray tuhe. will-rho doe term'inedhy the setting oLtbe variable ti dl'zthe potentiometer. It. much aslis theoase-in meats- 'Ehese vldeoeig'nale applied to the control electrode oi the cathode ragtime will. howeverhave edirect-currentooniponent-producedhy the comstantl D.- G. voltaee drop'eoroeslthe or. I) due tothe space ourrentoi. the'tuhe 15. By Olnn'e law. it will beohvioue that the creator-the epooecurrent through the tube ii the greater will be the D. C. component 01' signal-applied; tween, the control electrode and cathode oi; the cethoderay tube.

Thisdspaoercumentthrqtlshthe tube I5 will be determined, in part, has the mount of bineon the wall-'01 alumna-thereof, andsthis-hiaednay be changed. both, h the nenipuiatiom oi the arm It on the potentiometer It. and by variation oi. the resistance presented by the resistor ll. er proper selection of components it is easily possible to arrive at a condition where by properly adjusting the variable resistor H at the factory for the desired degree of contrast. variation of position 01' the arm .13 on the potentiometer l! will-chance both the level oi the videoslanalsnndthelmountoibiasonthn cathode ray tulle control electrode in such a fashion that optimum contrast conditions Bidet for all-levels oi video clonal.

.Thstthisistruecanbcccentromcccnsiderw tlonoi'theopcrotionoithecircnit. Mmeasc.

reference condition that the or the image on the-screen oi the plcturetube 2! is brieht; An increase in hiasdn the tube de-.

creases the brightness oi "the acksrmmd and V108 verse.

An increase in space current flow.

through tube 15 increases the bias on the tube 2! and thus darkens the background. Suohan increase in space current flowtnroush the tuloo ll iscaused by moving the contact I upwardi Binoe this darkens the backs-round or the picture tube, it calls for a rise in the level or video signal tomainteina constant contrast. Itscen be that raising the contact It provides such an increasein video sis'm-l level. whether thi inissumcient to retain the contrast at a constant value depends upon the amplification motor 0! the tube It and the circuit Parameters includfinlthcvaluesoithe various resistors. Re-renting now to Fla. 2. there is illustrated a second embodiment .of the instant invention wherein the arrangement of E13. 1 is connected conductiweiy to the output of the second detector circuit oi the videcchannol oi. a television receiver. The control electrode ll 01' the tube "II is connected to the arm I; oi'the potentiometer 'i 2 as in the Fla. 1 arrangement. The unsrounded 'end' ii o! the potentiometer it, however is directly connected to the wthode it of a diode diccharce'tuhe ID, the anode lll oi which is connected to a. source 8! ct intermediate-trewave sisnals through a condenser 82. A

"parallel resonant circuit ltituned to the ireque'ncy oi the intermediate irecuency source ti,

between $116 'mode 30 and a load 3|. The load resistor 84 provides a connection from the resonant circuit 88 to the oath- 'ode 28 or the ,diode tu e. Areletircly 1988B lay-pass condenser I! is end or the parallel resonant circuit 83 to crowd.

In operation. the moment shown in Fig.

from the lower 2 provides s method oi the video oute tin-ouch a condenser. This I 0. component oi;the .video high-miitmt llimcnt to invention is not thereto. For est-mole. a triode tube has heenshown as the driver to: the cathode my tube; this couldfof course. be

current component (it rid icnali is 4 replaced by any one ci a number 01 other types of tubes without char-lain: the basic principle or operation oi the instant device. For a definition of the limits of the invention reference will he had primarily to the appended claims. What is claimed is:

1. In e. television circuit comprising a video mplification. channelisnd a picture tube. said amplification channel comprising a final stage having a control electrode, on input circuit and on anqdecirouit and said picture tube having a control electrode and a cathode; a. iced impedonce in said anode circuit; means connection said control electrode and cathode oi said picture tube-across, said impedance; a source oi piste supply voltage for said final stage and a voltage divider in said input circuit. said voltage divider beingconnected between said source and the control electrode of said iinai stage and being variable to sinmltaneousiy vary the amplitude 01' the video siznaland the" magnitude of the control electrode bias or said stage. there!!! controllingthe ccntrestoi'thepictu're onsaidpicturetuhe while maintaining constant the block level thereof.

2 .In otelcvision circuit: a video amplifier; a potentiometer-in the input circuit at said amplifi'ier; means applying the envelope 0! a video signal across saidpotentiometer: an impedance connected in the output circuit of. said amplifier; a'picture tube having a control elecin'ode and a cathode: mesnsconnecting said control electrode and said cathode across said impedance. a source oi plate sunl llwvoltogeior said amplifier. and a variable impedance connected between said source and saidpotcntiometer.

3. Inateievision receiver: a irideonmpliilcr: a. potentiometerm the input circuit 01' said ampliner; nirideo detector circuit, a load impedance in said detector circuit. asource piste-simply voltage tor said amplifier; a variable impedance connected between said source and said potentlometcr: means direc connecting said load impcdance to a'point between said variable impedance and said potentiometer; .a picture tube ,h ins eoontrol electrode and a cathode, a load impedanceconnected in the output circuit of said cmpliflerfand. means connecting said control electrode and'cathcde across the last named load impedance. r i FRANK R. NORTON.

REFERENCES CITED The following references are of record inthe his. or this patent:

UNITED STATES PATENTS Number Name Date 1,141,343 Campbell Dec. 27, 1988 2,240,136 Geieer Apr.- 29, 1941 2,246,409 Miller June i0, 1941 2,252,746 Wfllans Aug. 19, 1841 2,308,997 Miller Jan. 19, 1948 2,388,809 Schade Nov. 28, 1944 FOREIGN PATENTS Number Country Date 477,483 7 Great Britain Dec. 20, 1937 

